The present invention relates to a stretchable liquid crystal polymer (LCP) composition suitable for use in the production of a variety of shaped articles including films, fibers, multilayer laminates and blow molded forms. This invention also relates to a process for stretching a multilayer laminate where one of the layers is made from the stretchable LCP composition.
Anisotropic melt-forming polymers, also known as liquid crystalline polymers or xe2x80x9cLCPsxe2x80x9d, are well known in the art. Anisotropic melt-forming polymers exhibit a parallel ordering of molecular chains in the melt phase and are also termed xe2x80x9cthermotropicxe2x80x9d liquid crystal polymers. Many of these materials are wholly aromatic in nature.
Commercially available LCPs are known to have many excellent physical properties compared to conventional polymers, such as higher tenacity and modulus. LCPs are also excellent barriers to transmission of chemicals, gases and water vapor. The LCPs can be used as gas barrier layers in conjunction with other thermoplastic materials to reduce the transmission of gases in packages. However, one problem that conventional LCPs have is their inability to be used in applications that require a post orientation process such as fiber stretching, film orientation and thermoforming. Conventional thermoplastics that are not stretched or drawn tend to have poor physical properties such as low tenacity and modulus. These conventional thermoplastics must be heated above their glass transition temperature, typically between 130 and 160xc2x0 C., and stretched in order to orient the polymer and improve their physical properties. The problem with conventional LCPs is that they can not be used as barrier layers for oriented packaging because they do not stretch well at temperatures typically used for conventional thermoplastic orientation processes.
Therefore, it is an object of the present invention to provide a liquid crystal polymer that is stretchable at temperatures typically used in thermoplastic orientation processes for the packaging industry.
This and other objects of this invention will be apparent from the following detailed invention.
U.S. Pat. No. 6,132,884 to Linstid III et al. discloses a stretchable LCP containing units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, at least one aromatic diacid and an aromatic diol, a portion of which is 4,4xe2x80x2-biphenol, resorcinol and at least one additional monomer that provides the resulting polymer with selected meta linkages.
U.S. Ser. No. 09/483,765 to Linstid IlIl et al. describes a stretchable LCP containing units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, an aromatic diacid, at least a portion of which comprises 2,6-naphthalene dicarboxylic acid, and an aromatic diol and/or aromatic aminophenol component, at least a portion of which is 4,4xe2x80x2-biphenol and resorcinol.
U.S. Ser. No. 09/483,103 to Linstid IlIl et al. describes a stretchable LCP containing units derived p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, at least one aromatic diacid and at least one aromatic diol and/or aromatic aminophenol component, at least a portion of which is 4,4xe2x80x2-biphenol and one or more aromatic monomers, excluding resorcinol, that provide the polymers with selected meta linkages.
U.S. Pat. No. 5,656,714 discloses an amorphous and what are termed xe2x80x9csemi-crystallinexe2x80x9d polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 4,4xe2x80x2-biphenol, and resorcinol. The polymers exemplified by U.S. Pat. No. 5,656,714 vary in terms of their degree of crystallinity; some, but not all, of these polymers are highly stretchable.
U.S. Pat. No. 4,910,284 to Hijikata et al. describes polymers consisting of 35 to 90 mole % of a p-hydroxybenzoic acid moiety, 0.5 to 30 mole % of a 6-hydroxy-2-naphthoic acid moiety and 0.5 to 30 mole % of a m-hydroxybenzoic acid moiety. The patent does not describe that any of the compositions are stretchable at temperatures typically used in the packaging industry.
U.S. Pat. No. 4,337,190 to Calundann describes a polymer consisting of 6-hydroxy-2-naphthoic acid moiety and m-hydroxybenzoic acid moiety.
U.S. Pat. No. 4,130,545 to Calundann describes a polymer consisting p-hydroxybenzoic acid moiety, 2,6-naphthalene dicarboxylic acid moiety, m-hydroxybenzoic acid moiety, and an aromatic diol moiety.
The objects of the present invention are achieved by providing a stretchable polymer consisting essentially of recurring units I, II and III wherein recurring unit I is: 
recurring unit II is: 
and recurring unit III is: 
wherein said polymer has a composition within region A of FIG. 1.
This invention also provides a process for stretching a multilayer laminate comprising the steps of: (a) providing a multilayer laminate comprising a layer of a thermoplastic and a layer of a polymer consisting essentially of recurring units I, II and III described above where the polymer has a composition within region B of FIG. 2; and b) stretching said laminate greater than about 100% elongation at a temperature greater than the first order transition point of said polymer and less than about 200xc2x0 C.